Provenance And tranSport PathwayS of mArine proxy-bearinG particlEs

Project Information

PASSAGE

Grant agreement ID: 101039348

DOI

10.3030/101039348

EC signature date 11 April 2022

Start date 1 September 2022

End date 28 February 2029

Funded under

• European Research Council (ERC)

Total cost

€ 1 499 766,00

EU contribution

€ 1 499 766,00

Coordinated by

AGENCIA ESTATAL CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS
Spain

Periodic Reporting for period 1 - PASSAGE (Provenance And tranSport PathwayS of mArine proxy-bearinG particlEs)

Reporting period: 2022-09-01 to 2025-02-28

Summary of the context and overall objectives of the project

Climate change has gathered increasing societal attention due to its potential future consequences for society. Understanding the nature and pace of climate change in the future requires robust and accurate information on past Earth’s climate changes, especially on short-term and abrupt climate variability. Knowledge on past short-term climate variability stems from different climate archives (e.g. three rings, speleothems, ice cores, etc.). Among these, marine sediment sequences are one of the most continues archives, while sedimentary particles encapsulate climate information and provide a wide array of paleoclimatic indicators or proxies. The fundamental assumption underlying most paleoceanographic investigations is that the environmental/climate signal encapsulated in marine sedimentary particles reflects that of the overlying water column at the time of formation. However, evidence indicates asynchronous synthesis and transport from distal locations for co-deposited sediment components. Such long-distance, secondary transport potentially introduces spatiotemporal biases in the derived climate reconstruction. Consequently, fundamental questions arise regarding the fidelity of paleoclimate records. Moreover, the magnitude of such temporal and spatial offsets likely varies in concert with hydrographic – and associated hydrodynamic – changes.
Given these limitations, two crucial knowledge gaps become apparent:
1) a comprehensive understanding of the influence of particle transport modes on the entrainment and deposition of allochthonous marine particulate material.
2) quantitative constraints on the impact of marine particle translocation on derived climate signals.
Specifically, this research will: (i) estimate the contribution of allochthonous/asynchronous material; (ii) constrain the extent and nature of the specific modes of particle transport; (iii) quantify their potential to bias derived climate signals; (iv) correct for distorted proxy records and reconstruct past hydrodynamic changes. We will develop cutting-edge methodologies for particle isolation and will apply state-of-the-art analytical techniques for compound-specific radiocarbon (14C) determination. The timeliness of this project is fostered by the recent advances in 14C detection for measurement of ultra-small samples. This work would provide a crucial advance in our ability to reliably interpret short-term climatic signals.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

In 2023, we carried out the oceanographic cruise PASSAGE23, during which we deployed two mooring lines with several sediment traps and hydrographic sensors that will sample settling particles and the hydrological variability of the SW Iberian margin for 1 whole year. This is the first successful deployment of mooring lines in this highly hydrodynamic region, a benchmark area for paleoclimate investigations that has been the focus of countless (paleo)oceanographic cruises. Yet, no information on the yearly oceanography of the water column of the region has been produced so far. We will retrieve these moorings 1 year later, during cruise PASSAGE24, to produce novel knowledge on the provenance and transport pathways of proxy particles derived from sediment trap material and hydrographic sensors.

We have established the BiG lab, the new Biogeosciences Laboratory born under the framework of the PASSAGE project. BiG is an Organic Geochemistry lab, aimed at processing marine sediments, soils, and plants to extract, purify, and analyze the organic compounds they contain. Here we conduct routine analyses in Organic Geochemistry to let the organic molecules tell their climate stories.

We have advanced our understanding of the origin of the organic matter in marine sediments and the processes that determine its redistribution and final deposition in the Western Mediterranean Sea and the adjacent Atlantic Ocean (SW Iberian margin). Our work provides fundamental information to evaluate the potential origin of the pre-aged organic carbon found in the SW Iberian margin in the next steps of the project. This work is the subject of our latest publication “Publication of Sources and Fate of Sedimentary Organic Matter in the Western Mediterranean Sea” published in Global Biogeochemical Cycles.

In collaboration with our colleagues at ETH Zurich (Switzerland), we have developed and implemented a new methodology to sort, purify, and radiocarbon date coccoliths based on flow cytometry, a technique grounded in medicine and biology whose application to paleoclimate is still a budding field.

Our preliminary results on radiocarbon ages of coccolith-size classes provide unique insights into the differential impacts of specific hydrodynamic processes on coccoliths. Such a relationship informs about the complex hydrodynamic influence on the paleoclimate information extracted from these proxy particles, a relevant milestone of this project.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The novel flow cytometric sorting approach we have developed to radiocarbon date coccoliths opens up new opportunities for coccolith geochemical analyses and will be the starting point for future innovative applications.

To the best of our knowledge, our radiocarbon ages of coccolith-size classes are the first radiocarbon measurements on coccolith samples isolated from complex matrices. Our work in progress indicates that some coccolith species are more suitable for geochemical analyses and paleoceanography/paleoclimate inferences than others.